Mimosa Plant (Mara)
Mara Desso
Principle(s) Illustrated
Nyctinastic movement.
Adaptations to environment
Turgor pressure
Standards
HS-LS2-7.
HS-LS4-2.
HS-LS4-4.
Design, evaluate, and refine a solution for reducing the impacts of human activities on the environment and biodiversity.
Construct an explanation based on evidence that the process of evolution primarily results from four factors: (1) the potential for a species to increase in number, (2) the heritable genetic variation of individuals in a species due to mutation and sexual reproduction, (3) competition for limited resources, and (4) the proliferation of those organisms that are better able to survive and reproduce in the environment.
Construct an explanation based on evidence for how natural selection leads to adaptation of populations.
Questioning Script
Prior knowledge & experience:
Students likely already have heard of the venus fly trap, which is a plant that can move to consume prey. They also probably do not associate plants with movement from past experiences.
Root question:
Why does the mimosa plant move when touched?
How does the mimosa plant move when touched?
Target response:
Why does the mimosa plant move when touched?
The plant likely moves for two reasons. First, if an insect lands on the plant to eat it and the plant moves, the insect will likely be scared away or fall off the plant and move onto a plant with less defense. Second, at night, when the leaves close up, it may prevent water loss.
How does the mimosa plant move when touched?
When stimulated, either by absence of light (night time) or touch, the plant moves its leaves through altering the turgor pressure at the base of the leaves. The change in turgor pressure is due to the movement of potassium K+ ions out of the plant cells. This changes osmotic pressure at the base of the leaf as water also moves out of the plant cells and causes the collapse of the leaves inwards.
Common Misconceptions:
Students may think that the plant has a central nervous system. You can have a discussion with students about the similarities between the release of K+ during the plant movement and how our nerve cells send signals using Na+/ K+ ion movement. This will help them realize that this is a similar but very different process from our own nervous system.